CONCRETE

Air-Entrained Concrete

Concrete with deliberately introduced microscopic air bubbles for freeze-thaw + workability

Also calledair entrained concreteair entrainmententrained airair entraining admixtureAEA concrete
Related on InfraLens
CODES
IS 456IS 9103
Definition

Air-entrained concrete contains billions of deliberately introduced, stable, microscopic air bubbles (typically 4-7% by volume) created by an air-entraining admixture conforming to IS 9103. The disconnected bubbles relieve the internal pressure of freezing pore water, dramatically improving freeze-thaw and de-icing-salt durability, and they also improve workability and reduce bleeding and segregation.

The trade-off is a strength reduction of roughly 5% per 1% of entrained air, so mixes are re-proportioned to compensate. In India it is mainly specified for high-altitude Himalayan and cold-region structures (Ladakh, J&K, Himachal high passes) subject to freeze-thaw cycles, and sometimes for improved pumpability/finish. IS 456 covers its use; air content is verified by the pressure-meter test on fresh concrete and must be controlled within a tight band.

Where used
  • Freeze-thaw exposed structures (Himalaya, cold regions)
  • De-icing-salt environments + hill roads
  • Improving pumpability + finish of lean mixes
  • Reducing bleeding/segregation in flat work
  • Durability spec for high-altitude infrastructure
Acceptance / threshold
Air-entraining admixture per IS 9103; entrained air typically 4-7% verified by pressure-meter on fresh concrete; mix re-proportioned for the ~5%-strength-loss-per-1%-air effect, used per IS 456.
Frequently asked
Why is air entrained into concrete?
The microscopic bubbles give freezing pore water room to expand, greatly improving freeze-thaw and de-icing-salt durability; they also improve workability and reduce bleeding.
Does air entrainment reduce concrete strength?
Yes — roughly a 5% strength loss per 1% of entrained air. Mixes are re-proportioned (lower w/c) to recover the strength while keeping the durability benefit.
Related terms
Concrete Admixtures
Plasticizers, accelerators, retarders per IS 9103
Slump Test / Workability
25-150mm slump per application (IS 1199)
Guniting (Dry-Mix Shotcrete)
Dry cement-sand mix conveyed by air + hydrated at the nozzle, sprayed onto a surface
Concrete Curing
Min 7 days for OPC, 10 days for PPC, 14 days for sulphate-resistant
Laitance
Weak, porous layer of cement fines and water on concrete surface. Must be removed before next pour to ensure bond.
Segregation of Concrete
Separation of coarse aggregate from cement paste due to over-vibration, drop height >1.5 m, or low cohesion.
Self-Compacting Concrete (SCC)
Highly fluid concrete that flows under its own weight, fills formwork, and consolidates without vibration.
High Strength Concrete (HSC)
Concrete with characteristic strength above M60. Requires silica fume, low w/c (<0.35), and quality aggregate.
Bleeding of Concrete
Upward migration of mix water to the concrete surface. Excessive bleeding causes weak top layer, dusting.
RCC (Reinforced Cement Concrete)
Concrete with steel reinforcement. Per IS 456:2000.